Published: 09/05/2023

The Effect of Recreational Cannabis Legalisation on Rates of Traffic Injury

Road traffic injuries are one of the leading causes of death, globally, in people aged 5 to 29, as well as one of the top three leading causes of injury-related hospitalisation in Canada. Identifying methods to reduce the risk of traffic injury is, therefore, a major consideration. Driving under the influence of alcohol and/or other drugs is a particular health concern in many countries around the world. As more countries consider alternatives to the prohibition of cannabis, it is vital to understand the potential effects on the rates of road traffic injury.

Canada introduced a nationwide enactment of recreational cannabis legalisation in 2018, granting increased access to cannabis products. Similar legislation was introduced in Uruguay in 2013 and in several US states since 2012. Evidence demonstrates that heavy cannabis use can cause impaired motor function, increased reaction time, and risky decision-making. These responses may increase the risk of serious injury or death from road traffic accidents when driving whilst impaired, after having consumed cannabis. Therefore, the effects of cannabis legalisation on the rates of road traffic injury and fatality have become a primary focus in recent years.

Current Findings

To date, the results of injury-related studies have been mixed; however, three studies identified a significant increase in traffic fatalities in the US and Uruguay, three found an increase after recreational cannabis legalisation only in Colorado. Two further studies did not find any significant changes in traffic fatality in US states after recreational cannabis legalisation.

While recreational cannabis was legalised in Canada in 2018, only one injury-related study has thus far been conducted. This study, published in 2021, found no evidence of significant changes in weekly counts of non-fatal traffic-injury emergency department (ED) visits associated with cannabis legalisation (based on figures from 2015-2019). The authors of a more recent study aimed to measure the impact of Canada’s recreational cannabis legalisation and the subsequent COVID-19 lockdowns from March 2020 on rates of ED visits and hospitalisations for traffic injury.

The global COVID-19 pandemic and subsequent lockdowns and further restrictions were responsible for a significant decrease in the number of vehicles on the road. During this period, a decrease in all injury-related ED visits was recorded globally; however, the most significant change was for traffic-related injuries (between 48-50% worldwide). Furthermore, rates of cannabis use have also been found to have increased in Canada in this period, with 40% of cannabis users in the country reporting an increase in consumption.

It is important that assessments of changes to road traffic injury in Canada since recreational cannabis legalisation (RCL) take these factors into account.

Design and Methods of the Study

The authors of the current study aimed to “assess the impact of RCL in Canada on rates of ED visits and hospitalizations for motor vehicle and pedestrian/cyclist incidents, and subsequently assess the impact of COVID-19 lockdowns after March 2020 on these outcomes.”

The researchers analysed population-based aggregate data from the Canadian Institute for Health Information (CIHI). They measured ED visits using CIHI’s National Ambulatory Care Reporting System (NACRS) for Ontario beginning January 2010, and Alberta beginning April 2010. Hospitalisations were measured using CIHI’s Discharge Abstract Database (DAD), with mandatory reporting across Canada beginning January 2010, except Québec.

Pre-RCL data period was January 2010 to September 2018. The post-RCL data period was October 2018 to February 2020, and the post-COVID period was March 2020 to March 2021.

Results of the Study

The population-based administrative databases used in this study are representative of over 36 million people across Canada. This data was used to assess the effects of recreational cannabis legalisation and COVID-19 on the rates of emergency department visits and hospitalisations for motor vehicle and pedestrian/cyclist injury.

The Effect of RCL on Traffic Injury ED Visits

Overall, the researchers identified no statistically significant changes in the rate of ED visits for motor vehicle or pedestrian/cyclist injury after the legalisation of recreational cannabis in October 2018. The authors theorise that the use of different outcome measures (fatalities compared to ED visits and hospitalizations) may explain why these results did not match the findings of US studies which concluded that rates of traffic fatalities increased after legalisation.

Furthermore, previous US studies found a change in traffic fatality in Colorado only and not in other cannabis-legal states. It is possible that jurisdiction-specific factors such as cannabis retail restrictions and driving laws in US states are important considerations when comparing data to Canada. The researchers also consider that their data may be associated with the effects of public health measures in Canada since RCL implementation which could have contributed to “a heightened awareness of the risks of cannabis use for new and previous users.”


This study provides a useful overview of the effects of cannabis legalisation on rates of emergency department visits and hospitalisations related to road traffic accidents in a legal cannabis jurisdiction. The authors conclude that these findings provide a useful baseline for future studies which they suggest should consider cannabis-related injuries specifically, and how RCL has affected rates of traffic injury for specific at-risk populations, such as young males.


Share this article